body {
  margin: 0;
}
ul {
  margin: 0;
  padding: 0;
  list-style: none;
}
a {
  color: inherit;
  text-decoration: none;
}

.box {
  width: 800px;
  margin: 100px auto;
  text-align: center;
}

.list {
  width: 800px;
}

/*in为选项卡普通状态，默认不显示*/
.in,
.in_active {
  display: none;
  height: 200px;
  font-size: 25px;
  line-height: 200px;
}

/*in_active为选项卡选中状态，选中后显示*/
.in_active {
  display: block;
}

.conList {
  text-align: center;
  line-height: 50px;
}

/*con为按钮普通状态，默认无轮廓*/
.con,
.con_active {
  outline: 0;
  border: 1px solid skyblue;
}

/*con_active为按钮选中状态，选中后有1px的黑色轮廓*/
.con_active {
  outline: 1px solid black;
}

button {
  background-color: aqua;
}